At risk of changing this thread (somebody feel free to start a new one, if this one gets rolling) here's my cut on Gross Anatomy:
First: Do not approach medical school with the "what's the least I know to become a doctor" approach. You patients will not come to you only with problems that were on the test. The short answer is you will need to know everything (all the bones, all the muscles, all the nerves, etc.) Okay. Enough motherhood.
The long answer, however, is that you can concentrate on the more significant anatomical structures. Our anatomy class has been mostly major structures (the primary muscles that move things, nerves that innervate them, or have autonomic significance and so on) and structures with a significant clinical correlation. (For example, a nerve that is easily damaged, and the accompanying clinical signs).
Personally, I think you should enjoy your summer and *NOT* study anything. Realistically, you're not going to be able to reduce your study time by very much even if you bust your ass during the summer learning stuff. If you just can't stand not having your head buried in a book, I'd work on the bones. They're pretty straightforward, and most atlases provide decent depictions. Just realize that you miss out on the 3D aspects of the bones, but if might be helpful to memorize the names of the bones (and more importantly, the features of them)
Regarding the Common Textbooks and Atlases associated with Gross Anatomy:
Netter's Atlas: Great pictures. This seems to be the standard by which all others are judged.
Rohen, J.W. et. al. "Color Atlas of Anatomy: A Photographic Study": As the name implies, this is a photographic atlas, which is a lot more effective in giving you a feel for what things will "really" look like. (BTW, don't think that your own dissection will look anything like the pics in the Rohen boook...I swear the bodies they dissected are still warm, they look so good.)
Grant's Atlas: Personally, I liked this atlas better. In addition to the nice drawings, there are tables of muscles, nerves and arteries which are helpful in organizing and memorizing the information.
Moore, et. al. "Clinical Anatomy": This is the book I would buy if I could do it all over again. It has very similar pictures to the Grant atlas, plus a ton of great clinical pictures, diagrams and explainations.
Moore, et. al.: "Essential Clinical Anatomy": This is the readers-digest version of the Clinical Anatomy book. I found it helpful for taking into the Anatomy lab when studying. If it got covered in formaldahyde (or worse) I didn't mind if it got ruined.
There are obviously more, this is just a list of the ones that I used over the past semester.
If I could buy only 1, it would be the Moore "Essential Clinical Anatomy." If I could buy 2, it would be the Moore book and the Rohen Atlas. My 3rd choice is the Netter atlas, just out of principle.
However, what I recommend is that you take the summer off, and when school starts for you, go to the medical library and check out each of the above, and study out of them for the first couple of weeks (your library will probably have several copies on reserve) and then go out and buy the one(s) that you like the best.
<sigh> Sorry this is so long, but I haven't the time to make it any shorter.
Hope this helps.
Cheers,
-sb